The Sky's the Limit

Large parts and tooling thrive in precision job shop

Job shops that serve aerospace, military/defense, and commercial aircraft industries are always in for a challenging business ride as programs and projects emerge, mature, and eventually end.

These high-tech contract manufacturers must develop, maintain, and continually improve their machining and fabricating expertise to win new business to replace one-off, short-run, and prototype assignments for tooling and complex components. Production runs, if any, are usually not greater than single-digit volumes in any given month.

Boeing's 787 Dreamliner, which is an all-composite aircraft, has breathed life into the supply chain for the aerospace industry in southern California and in high-precision manufacturing shops around the world. While the majority of manufacturing will be done overseas, the assembly will be done by Boeing in the US.

The all-composite construction of the Dreamliner, and Airbus's conversion of the A350 to composites and the looming demand for the giant A380, have created a huge demand for tooling, assembly jigs and stations, and the composite parts themselves.

For a high-precision job shop like Stadco Inc. (Los Angeles), a manufacturer of some of the largest examples of Invar tooling used in the manufacture of composite parts, the surge in commercial aircraft manufacturing has brought growth and multiplied its opportunities in the global market.

As a result, over the last 18 months, Stadco has leveraged its manufacturing expertise, earned over years of experience in high-tech manufacturing, to win new business and contracts from a variety of offshore customers.

Founded in 1941 as a tool and mold manufacturer and acquired by its current owners in 1981, Stadco has built its reputation in this highly competitive market machining and fabricating some of the most demanding tooling and workpieces for the aerospace industry.

Stadco has ISO 9001:2000 and AS-9100B certifications, which apply to high-precision design and manufacturing of complex tooling and composites for the aerospace, defense, and commercial industries. It is also certified to MIL-Q-9858A and MIL-J-45208A, as well as ASTM, ASME, AWS, ANSI, and MIL welding standards.

"Our business is divided into three major areas," explains Douglas A. Paletz, Stadco president, "tooling, which was the beginning of the company, complex machined parts, and large complex fabrications. Today, about half of our business is commercial and half is military/defense-related with about 60% of the business in tooling and 40% in parts."

Stadco typically supports major primes, the direct airline manufacturers and their sub tiers. "We support one-off programs or projects for national missile defense systems, and we do complex machining and fabrications for universities and research laboratories," Paletz explains.

Manufacturing capabilities that Stadco has developed to serve these diverse industries and markets include:

Five-axis electron beam (EB) welding of aluminum, steel, titanium, and other exotic refractory metals in the largest such chamber in North America, and

Total Quality Management and control and inspection with CMM, Faro Laser Trackers, NDT, and X-ray.

Like most high-tech manufacturers, Stadco is continually challenged to fill it ranks with qualified people. "The number one challenge of our manufacturing business is getting qualified people in administrative jobs, as well as in the factory positions," says Paletz. "Average age of our factory people is now over 50, making it a challenge to continue to operate at the absolute top level of machining skills."

The competition for qualified people in southern California is a challenge. "Our approach is to bring people in as trainees and begin teaching them the business from the ground up. Our hope is that once they have gone through the various functions, we'll be able to retain them," says Paletz, who points out that the average tenure of employees at the company is 17 years.

As a result, Stadco has revived its apprenticeship program to enable it to meet its staffing requirements. "Trainees work in every one of our major machining and manufacturing functions. For example, our electron-beam welder operator was hired in and began his career with us in maintenance and was trained and worked his way into his current position," Paletz explains.

For job shops like Stadco, it isn't always easy to point to their products, including parts or tooling they have produced. They are often part of other structures, assemblies, or even weapon systems. In Stadco's case, components may be embedded in complex systems that are essential to space-bound launch vehicles or are permanent parts of orbiting satellite platforms or earth-bound research systems. Or they may be the sophisticated Invar tooling that is used to produce the composite components that keep commercial and military aircraft flying overhead.

In aerospace, Stadco had built the master gages for nearly every launch vehicle made since the early 1960s, including the Titan, Polaris, Poseidon, Trident, PeaceKeeper, and the Space Shuttle solid rocket motor. The company is one of few firms in the world capable of precision machining large round, curved, cylindrical, and convex launch vehicle components such as nose cones and motor cooling jackets.

A walk through Stadco's 300,000 ft2 (27,871 m2) manufacturing facility provides a good insight into what it takes to manufacture—machine and fabricate—large complex tooling and parts for the global aerospace, defense, and commercial aircraft industries.

Most of the tooling that it machines and fabricates is in support of composite part manufacturing. All critical manufacturing processes are maintained in-house—detail fabrication, egg-crate substructure, bump forming of face sheets, welding, rough and finish machining, leak checks, laser checks, final assembly, and packaging.

It makes molds, lay-up fixtures and bond fixtures, as well as forming tooling, assembly and jig tooling. Machining is performed on tooling fabricated from Invar, aluminum, steel, or exotic materials.

Stadco specializes in manufacturing tooling made from Invar, both grades 36 and 42, which is a versatile material that can be used in any composite tooling system. The material is especially valued where the end product is required to have low weight, be structurally sound, and have a net or near-net shape. Stadco has designed and manufactured Invar tooling as long as anyone in the aerospace industry, with a proven record of providing very reliable, exacting tools.

For its machining, Stadco numbers more than 30 horizontal and vertical boring mills and five-axis contour milling machines in its main manufacturing facility. Its single largest work envelopes are found on three Giddings & Lewis four-axis boring mills, with work envelopes of 576 x 156 x 120" (14.6 x 3.9 x 3 m) X,Y,Z. Two of these machines are positioned side by side, utilizing the same runway. With one machine in park, the X-axis capacity of the other can be increased to 730" (18.5 m).

For the size of workpieces and tooling that Stadco produces, it has crane capacities of 30 tons (60 tons dual use) and tooling capabilities in excess of 100 tons (90.7 t).

The lineup of large-part machines reads like a who's who of large-scale machining. The latest additions to its equipment lineup are a TosHulin Powertrain 3500 double-ram VTL and a Jobs Jomax 265 five-axis gantry milling machine.

Workpieces to 25' (7.6-m) diameter are being turned on VTLs. Cones, spheres, cylinders, hemispheres, tapered mandrels, jig assemblies, and egg-crate holders—15 to 20' (4.6–6.1-m) long—for producing parts and components for virtually every kind of space-bound, air-carried, water-borne, or submerged vessel are being machined and fabricated.

The workpieces Stadco produces are typically medium-to-large in size with varying complexities. "Customers rely on Stadco for their more difficult parts and assemblies. We're not a high-volume production shop. A big rate for us would be several a month of anything. It tends to be short flow. We are involved in developmental work and low-rate production," says Paletz.

To its conventional welding capability, which includes JetLine semi-automatic TIG welding with Miller-Aerowave 375A power supply, Stadco has added an electron-beam welding chamber, said to be the largest in North America. The Sciaky electronbeam welder Model VX weld chamber has a work envelope of 248 x 70 x 54" (6.3 x 1.8 x 1.4 m) and a 60-kW–60-kV tilt gun with optics.

The EB welding machine has five-axis CNC control and is capable of weld speeds up to 100 ipm (2.5 m/min) and penetration to 5" (127 mm) in a single pass, with little or no distortion. The EB welder gives Stadco the ability to weld titanium and other refractory alloys such as zirconium, niobium, molybdenum, and tantalum, as well as Inconel, stainless, aluminum, copper, and precious metals. Additionally, Stadco is developing EB welded Invar tubing, this item will significantly improve the structural integrity of the tooling sub-structure while reducing the tooling weight.

The importance of the EB welding capability is in the metal-joining capability that it gives, the weight reduction that is possible, and the ability to achieve thin walls in some components.

The variety of its manufacturing assignments give a good idea of Stadco's ability to match machining and fabricating capabilities with the precision requirements of its diverse customer base.

The University of Rochester came to the company with a project for a specialized high-tech vacuum chamber that was to be used as part of a system to study inertial confinement fusion. The project required the use of all of the company's resources, including engineering, large and medium machining, welding, toolmaking, and quality assurance, as well as its ingenuity in engineering a solution for manufacturing and installing the chamber in an existing building.

The grating compression chamber for the University of Rochester was manufactured in seven modules with a completed length of 70 x 17' (21.3 x 5.1-m) square with each module weighing over 35,000 lb (15,876 kg). Stadco's design concept allowed the chamber to be manufactured in modular form, shipped in segments, and assembled on-site at the university. The clean room already existed and they didn't want any welding, fabrication process, painting or cleaning going on. It was able to do all the processes outside of the clean room, install with a seal, and bolt it together. The unit easily passed the high vacuum leak check. The project involved a lot of fabrication and welding. For each chamber there's something like 100,000 linear inches (2540 m) of weld on each module.

An aluminum target ball 4.5-m diam was fabricated for a project similar to the one at the University of Rochester. It also provided Stadco the opportunity to highlight many in its core competencies—machining, welding, assembly, lifting, and testing.

For the space station, Stadco machined, assembled, and performed the final closeout weld on the cylinder of a cryomagnetic vacuum case that goes on board to aid the search for black holes. The particle flange support ring, the machine cylinder conical flange, and an inner cylinder ring are machined and bolted together, except for a weld seam on the inner cylinder. They are all assembled and a final closeout weld is performed on the cylinder.

Combining the disciplines of EB welding and machining has given Stadco an entrée to a number of projects. For instance, three separate components made from titanium 6al 4v material are EB-welded together. Initially this part was "hogged-out" of a bar of titanium, Stadco provided a more reliable part and saved the program money through its innovative approach.

An aluminum hinge beam for a 787 is made out of a big chunk of aluminum. This developmental part was so complex Stadco was approached after several companies failed to meet the demanding program schedule. What's difficult is that you start out with a big solid block of material. The more material that you remove, the more stresses that are introduced into the material, and especially considering the complexity of the part, it wants to move.

For the large Trent 900 rear fan case engine, Stadco is tooled to produce titanium assemblies. The customer, Goodrich/Rolls Royce provides a forging that Stadco machines. Goodrich bonds a titanium honeycomb and sends the workpiece back to Stadco for final machining.

Whether it is large Invar tooling, complex machined parts, or intricate assemblies, Stadco is solicited for its expertise in machining, fabricating, and assembly capabilities.

This article was first published in the March 2007 edition of Manufacturing Engineering magazine.